1. Technical Field
The present invention relates to a technique for ejecting a fluid from an ejection head.
2. Related Art
Inkjet printers that eject ink onto a print medium to print an image have been widely used as image output means nowadays because they can easily print an image of high quality. When, instead of ink, various kinds of fluids (for example, a liquid having fine particles of a functional material dispersed therein or semifluid such as gel) that are each prepared so as to have a proper component are ejected onto a substrate by applying this technique, it is conceivable that various kinds of precision components such as an electrode, a sensor, or a biochip can be easily manufactured.
In such a technique, a special ejection head provided with a fine ejection port is used so that an accurate amount of fluid can be ejected at a correct position. The ejection head is provided with a drive element (for example, piezo element) connected to the ejection port. A fluid is ejected from the ejection port by applying a drive voltage waveform to the drive element. The amount or shape (for example, size of droplet) of the fluid to be ejected from the ejection port can be changed by controlling the drive voltage waveform to be applied to the drive element.
When an amplifying element such as a transistor is used for generating the drive voltage waveform, power consumption is increased because power is lost in the amplifying element (for example, collector dissipation of transistor). Therefore, a technique is proposed in which the drive voltage waveform is generated by storing different voltages in a plurality of capacitors and changing the capacitors at appropriate times to change the voltage without using an amplifying element (JP-A-2003-285441).
In the proposed technique, however, a large number of capacitors are required for ensuring the accuracy of the drive voltage waveform, which causes a problem of an increase in circuit scale. That is, since voltage is output by changing the capacitors each having a different voltage, the number of kinds of voltages to be output is limited to the number of capacitors. Therefore, a large number of capacitors have to be provided for ensuring the accuracy of the drive voltage waveform, resulting in an increase in circuit scale.